Not Applicable
Not Applicable
This invention relates to a control cabinet for a tablet press.
A system of a tablet pressing device, apart from the tablet press proper and other peripheral devices, includes a control cabinet in which all components and assemblies are contained for the electric activation of the tablet press and peripheral devices. Such control cabinets, as is common, have an enclosure of sheet metal and a door through which the interior of the enclosure and, hence, the individual elements are accessible in the control cabinet. For reasons of safety, the door of the control cabinet is usually closed and may be opened by authorized personnel only. This means, however, that troubles which arise in the control cabinet or are signaled therein are not available for immediate access if the authorized person is not nearby.
Therefore, it is the object of the invention to provide a control cabinet for a tablet press which allows a view into the interior of the control cabinet even when its door is closed, which is shielded against electromagnetic waves, and is easy to clean.
In the inventive control cabinet, the door board is completely of a transparent material. The door board is composed of at least three layers, i.e. two outer layers of sufficiently stable, transparent material such as acrylic glass and a netting of an electrically conductive material interposed between the acrylic glass panels. The netting is structured so as to not essentially prevent a look through the door board. Thus, an operator may readily take a glance at the inter of a control cabinet and see whether certain pilot lamps or the like are responding or signaling an alarm or an error situation.
As mentioned earlier, the door board is assembled from the elements described. A stabilizing border or the like is unnecessary. This has the substantial advantage that the control cabinet may have smooth surfaces continuously extending from outside, which is important for sanitary reasons.
Connected to the netting is a contacting device which links the netting to the enclosure. This usually consists of plate-shaped metal sheets and, hence, of conductive material. Such control cabinets have to be Faraday cages, i.e. to prevent electromagnetic waves from getting into and out of the control cabinet. This shielding action is performed by the netting in the door region with a need to conduct the netting to the enclosure in an electrically conductive manner as was mentioned above.
Several possible constructions are imaginable to connect the netting to the enclosure. According to the invention, one consists in that the inner panel has exposed a strip of the outer panel at its edge which includes the netting, if necessary, and that a contact element is connected to the associated portion of the enclosure which contacts the exposed portion or netting when the door is in its closing position. Preferably, the contact element is formed by a sealing strip of conductive material. It is imaginable to dispose the sealing strip around the whole door opening from inside and to cause it to engage an exposed portion of the netting each. This will only produce a contacting effect when the door is closed, but there will be no protection against electromagnetic radiation when the doors of conventional control cabinets are opened.
A particularly preferred solution according to the invention is that material is cut off from the side of inner panel and from the wire netting by a milling operation so as to expose the adjoining panel. The exposed strip, together with the edge of the panel from which material was milled off, is coated with a layer of a conductive material such as conductive varnish, especially a conductive silver varnish. A sealing strip of a conductive material sealingly engages the conductive layer and simultaneously makes an electric contact therewith. The conductive layer is conductively connected to the netting. Preferably, the sealing strip is formed as a box-like profile so that a wide-area contact is made with the conductive layer. Preferably, the sealing strip is in the hinge region of the door board, but may also be mounted on all of the four sides of the door opening as was explained above.
Alternatively, a pin of electrically conductive material extending through the door board may be provided, which is connected to the door hinge and to the netting, on its part. The pin may be a usual fixing pin which connects the hinge to the door board. For this purpose, the pin extends through a bore of the door board. In another aspect of the invention, an electrically conductive bushing may be disposed in a widened bore portion of one panel, which surrounds the pin and one front-end of which abuts upon the netting and the other end of which abuts upon the head of the pin with the length of the bushing being slightly larger than the thickness of the panel. This presses the bushing against the netting and, in turn, may provide an electric line to the enclosure via the hinge. It is understood that a similar contacting action is provided via the so-called sash fastener. What is normally understood by a sash fastener is a rotary pin having a lateral lug at its inner end, which when closed grips behind an edge of the enclosure, thereby keeping the door in a closed condition.